Methods of controlling and optimizing the production of chemical substances are well known. The control of parameters such as temperature, pressure, mixing conditions, relative volumes of the reactants, and the use of catalysts are generally well understood. Recently, much attention has been directed to the use of micro-scale reactors for both development and production of chemical products. These types of microreactors offer several clear advantages over more conventional macro-scale chemical production systems.
First, the control of chemical processes within very small reactors is much simpler than the control of the same process in a large-scale production tank. Safety is enhanced, as relatively small volumes of chemicals are processed within a single reactor. Thus, the severity of any potential accident involving a single microreactor is minimized. Once a reaction process has been developed and optimized in a microreactor, production in larger quantities can be enabled by replicating the microreactors in sufficient quantity so as to achieve the required production levels. If such reactors can be fabricated in quantity, and for a modest cost, industrial quantities of a desired product can be manufactured with a capital expenditure equal to or even less than that of a traditional chemical production facility.
This approach also offers a substantial improvement over conventional methods for moving from small-scale production to large-scale production. In the past, a chemical production process perfected in the laboratory using small volumes of chemicals often required considerable modifications to be made in the process when converting it to large-scale production, due to changes in process conditions. Such scale-up problems often cause frustrating and expensive delays in moving from research to production.
The pharmaceutical industry in particular engages in chemical research on many new chemical compounds every year, hoping to find a drug or chemical compound with desirable and commercially valuable properties. The research process is complicated, time-consuming, and costly. Discovering a new drug has been likened to searching for the proverbial needle in a haystack. Literally tens of thousands, and sometimes hundreds of thousands, of chemical compounds must be made and tested to find one that can achieve a beneficial result without prohibitive side effects.
Such a complicated process costs vast amounts of time and money. The Food and Drug Administration (FDA) estimates that, on average, it takes eight-and-a-half years to study and test a new drug before the agency can approve it for the general public. Drug companies spend $359 million, on average, to develop a new drug, according to a 1993 report by the Congressional Office of Technology Assessment. A company such as Hoffmann-La Roche, whose annual sales in the United States alone are about $3 billion, spends about $1 billion a year on research worldwide.
It has been recognized that microreactors are of tremendous potential use to the pharmaceutical industry. Aside from providing safety benefits, and providing the ability to ease the transition from research to full-scale commercial production, microreactors utilize small volumes of chemicals efficiently. Often the chemicals used in drug research are costly and unavailable in significant quantity. Thus, the ability to perform research using small volumes of chemicals efficiently is important.
It has further been recognized that end users of microreactors, whether in a research setting or a production setting, desire not just a microreactor, but an integrated system that enables an end user to easily and effectively exploit the full potential of microreactors. Just as many computer users purchase a complete computer system, rather than just the microprocessor, which is at the heart of a computer system, many research and production facilities will desire to purchase a microreactor system that enables the end user to efficiently produce a variety of desired chemicals in almost any desired quantity, by making changes in the system, to scale the production as appropriate.
At least one design for such an integrated microreactor based system has been investigated. A patent issued to Bard (U.S. Pat. No. 5,580,523) describes a modular microreactor that includes a series of reactor modules connected in fluid communication, each reactor module having a particular function. Bard specifically teaches that the plurality of microreactor modules are mounted laterally on a support structure, and that individual microreactor modules can be replaced as needed. These reactor modules disclosed in the Bard patent minimally include a reactor module, a separator module, and an analyzer module, and additional microreactor modules can be added in series or parallel. Bard specifically teaches that separate mixing modules and reaction volume modules are used. This patent also teaches that a variety of generic components, such as computerized controls, pumps, valves, flow channels and manifolds can be included in such an apparatus.
It would be desirable to provide a modular chemical production system that utilizes microreactors but offers additional flexibility to the user, beyond that of the Bard system. For example, it would be desirable for all of the components of the system, and not just the microreactor units, to be modular in design so that any component, such as a pumping unit, can be replaced as needed to produce either a different type of chemical product, or a different quantity of the desired chemical product, or to easily replace a defective component.
Furthermore, to reduce the number of modules required, it would be desirable to provide a reaction module in which the mixing of the chemicals reacting to form the desired chemical product is achieved within the same reaction module in which the chemical reaction between these chemicals occurs, so that a separate mixing module is not required. It would also be desirable for such a single reaction module to incorporate a microreactor that enables rapid diffusion mixing. Diffusion mixing can be achieved by forcing fluids to flow in a laminar flow pattern within small fluid channels and is characterized by being extremely rapid and efficient, more so than mixing achieved by creating turbulence or agitation. It would further be desirable to provide a reaction module in which the microreactor is replaceable, so that a different type of chemical product can be produced without requiring the replacement of the entire reaction module.
Another desirable feature of the microreactor modular system is a control module that includes an intuitive user interface, enabling a user to select from a stored menu of desired chemical products, so that after selecting a desired amount of a particular product, the user is only required to connect the system to a source of the required chemicals, and the control unit will control the system according to stored processing parameters, such as flow rates, temperature, and pressure, to produce the selected product.
A pump module in such a system should provide sufficient pumping capacity so that flow rates of reactants into the reaction module can be increased to the maximum capacity of the reaction module without requiring replacement of the pump module with a higher rated output pump module. However, should additional reaction modules be necessary within a system to further increase the quantity of product produced, the pump module should be configured to be readily replaced with a pump module capable of providing the required flow rate.
It would further be desirable for all the processing modules to have housings of a consistent size and shape. Any inlet and outlet ports incorporated into the housings of the processing modules should be located in the same positions on all the processing modules, and all connections between processing modules should be of a quick connect type to enable the rapid replacement or addition of processing modules when changing the configuration of the system. Such connections should preferably be self closing to prevent spills when processing modules are replaced. The user should have an option to select processing modules adapted for either parallel fluidic heat transfer or serial fluidic heat transfer, when temperature control of a chemical process is required.
Because many possible reactions that can be beneficially achieved using such a modular chemical production system involve pressure dependent reactions, it would also be desirable for such a system to include a throttle, such as a proportional valve, at the end of the reaction path. Closing the throttle will make the pumps in the pump module apply a higher pressure to the liquids, to maintain a constant flow rate.